There exists a variety of different stacked assemblies and structures in the context of electronics and electronic products.
The motivation behind the integration of electronics and related products may be as diverse as the related use contexts. Size savings, weight savings, cost savings, or just efficient integration of components and associated, potentially synergetic, functionalities may be originally sought for when the resulting solution ultimately exhibits a multilayer nature. In turn, the associated use scenarios may relate to product packages or food casings, visual design of device housings, wearable electronics, personal electronic devices, displays, detectors or sensors, vehicle interiors and vehicle electronics, antennae, labels, etc.
Electronics such as electronic components, ICs (integrated circuit), and conductors, may be generally provided onto a substrate element by a plurality of different techniques. For example, ready-made electronics such as various surface mount devices (SMD) may be mounted on a substrate surface that ultimately forms an inner or outer interface layer of a multilayer structure. Additionally, technologies falling under the term “printed electronics” may be applied to actually produce electronics directly and additively to the associated substrate. The term “printed” refers in this context to various printing techniques capable of producing electronics/electrical elements from the printed matter, including but not limited to screen printing, flexography, lithography and inkjet printing, through a substantially additive printing process. The used substrates may be flexible and printed materials organic, which is however, not always the case.
The concept of injection molded structural electronics (IMSE) actually involves building functional devices and parts therefor in the form of a multilayer structure, which encapsulates electronic functionality and possibly other functionality.
In an IMSE process different features of desired function may be first applied to a substrate film. Then the film may be inserted in an injection molding cavity, where hot melt state material is injected upon the film or between the films in the case of several ones, thus becoming an integral part of a resulting multilayer structure.
One interesting characteristic of IMSE is also that the electronics is often, not always, manufactured into a 3D (non-planar) form in accordance with the 3D models of the overall target product, part or generally design. To achieve desired layout of electronic or other elements on a substrate and in the associated end product, the electronics may be still provided on an initially planar substrate, such as a film, using two dimensional (2D) methods of electronics assembly, whereupon the substrate, already accommodating the electronics, may be optionally subsequently formed into a desired three-dimensional, i.e. 3D, shape and subjected to overmolding, for example, by suitable plastic material that covers and embeds the underlying elements such as electronics, thus protecting and potentially also hiding the elements from the environment.
In some use scenarios, space constraints limit the amount and nature of functionality that can be integrated in multilayer structures including IMSE structures.
For example, various functional features to be integrated in a common structure may require considerable space such as installation surface to first of all accommodate the associated physical element or elements, and secondly, to simultaneously maintain necessary distance between other features in favor of e.g. reducing mutually induced or externally coupled noise and thus improving signal-to-noise ratio so that inaccurate, unreliable or otherwise less-than-optimum operation such as erroneous measurements or so-called false positives (false detections of user input) could be avoided in different applications including sensing solutions.
As there may be noisy features that cause e.g. electromagnetic disturbances to the environment while there may also be features whose proper operation is particularly sensitive to disturbances, especially the integration of these two feature types may turn out challenging. Compensating noisy environment with increased size of sensitive features obviously results in even bigger space consumption related issues. Occasionally, part of the integrated features such as electronic features should remain closer to external environment such as use environment of a concerned integral structure, whereas it would be beneficial to situate some other features closer to e.g. a host device or host structure accommodating or connecting to the multilayer structure, whereupon successfully combining such objectives may be laborious, if not impossible, especially in the context of traditional, planar and stiff electronic designs and limited space with only complex shapes available for incorporating the features.
Sometimes by certain design choices such as the use of low-noise electronics (e.g. linear LED drivers instead of switched ones) the magnitude of disturbances caused may be reduced at the cost of other factors such as energy efficiency, heat generation, battery life, reduced functionality (e.g. no LED dimming). In some scenarios, operation of multiple features intended to jointly establish a functional ensemble may further suffer from sub-optimal, such as too short, distances therebetween. In some scenarios, several electrically functional conductive features are to be superimposed, which requires the use of e.g. dielectric layers as intermediate layers. Accordingly, the number of processing phases may considerably increase, while different undesired issues such as crosstalk may still emerge and also physical layout design of the structure be ultimately subjected a multitude of annoying restrictions, also potentially negatively affecting the overall usability of the resulting product. Yet, when features are tightly packed, also accidental activation thereof and issues arising from thermal management easily become real problems.
In some use scenarios, material deflection may be desired to enhance e.g. the sensitivity of self-capacitive or force sensing solutions, whereby air cavities could be included in the structures to enable such. The use of air cavities may however cause a variety of problems such as material compatibility issues and tendency to delaminate the integrated structural layers from each other.
Further, certain materials such as metallic or other highly conductive materials cannot be utilized as overlays as they may effectively prevent correct functioning of the underlying functional features. Correspondingly, the underlying features have set limitations to aesthetic and visual properties of the structure that might well establish exterior or otherwise visible, potentially tactile, surfaces in a myriad of end products.
Still, e.g. in different sensing solutions, electric, magnetic or generally electromagnetic fields may be generated and measured to detect selected target quantities and qualities. However, controllability of the strength, dimensions, shape and alignment of such fields may remain poor, which negatively affects also spatial sensing resolution and achieved, effective signal-to-noise ratio, for instance. Shielding from external electrical disturbances or different physical or chemical phenomena may further turn out challenging. Further, effective power distribution has in many scenarios caused trouble due to a limited conductivity of e.g. additively manufactured conductor materials.
Still further, in some occasions it has been found tricky to include several conductive and e.g. galvanically connected layers, or generally features, in a common structure as accurate positioning and alignment of the concerned features themselves or required connection elements is difficult and the obtained quality of connection, such as electrical connection, between the multiple layers may remain somewhat sub-optimal.